Means for working microphones in parallel.



- W-ZZnes-se R. GOLDSCHMIDT. MEANS FOR WORKING MICROPHONES IN PARALLEL= APPLICATION FILED 001. 1, 1912.

1,088,018.. *Patentedrebfzg 1914,

PATENT OFFICE.

RUDOLF GOLDSCHMIDT, OF BERLIN, GERMANY.

MEAN FOR WORKING. MICROPHONES IN PARALLEL.

Application filed October 1, 1912.

Z '0 all when), if; m (13 come-1");

Be it known that I, Renew GoLDscHMio'r,

a citizen of Germany, residing at Berlin,

ener y required for transmitting the soundv more particularly for long distance, is increased accordingly. It was hitherto considered unfeasiblc to connect microphones in parallel, owing to the fa ct that it is practically impossible to build not even two microphones which are alike from the start and remain so during prolong d use, as to operate with absolute uni't'orniii Ac cording to my invention this d'i liculty is effectively ovcrcou'ie by the interpolation of choking coils into the i'nicrophone circuits which equalize the di'tl crences in current dis tribution caused by the uneven operation of the microphones.

In the accompanying d "awin lfigure 1 is a wiring diagram showing my invention applied to two microphones; Fig. l a similar diagram showing the invention applied to three microphones, and Fig. a wiring diagram showing a modified form of the invention applied to three microphones.

deterring to Fig. l. the letters M and M, indicate a. pair of microphones which are l() 'ul'0(l at one trimsuiitting station, to be influenced by a c mmon sound wave. Microphone 3i. and i i, are connected in series with choking coils D l), respectively, the parts 1%,. D, and M 1),. being in turn connected in parallel. Choking vcoils D D are relatively so arranged or wound upon a common iron core C that their magnetizing c-tl'eets produced by the current flowing lhcrcthrough have the tendency to become neutralized woen equal currents pass therethrough. A cmisiderablc choking etiect. or inductive resistance however obtained, when owing to the dit fcreuces of the microphones, which passes the choking coils in series, the parts M, D,. 1),, M, constituting a closed circuit.

If more than two microphones are to be connected in parallel, they may in pairs be rendered uniform in working in manner Specification of Letters Patent. I

a compensating current is produced Patented Fehfii. i914. Serial No. 723,333.

analogous to that described with respect 'to Fig. 1, whereupon the operation of said pairsis rendered uniform by correspondingly coupled choking coils.

In Fig. 2 three microphones M M M, are illustrated which are directly connected to choking coils D D. D, respectively. The latter are in turn connected to choking coils D, D D whereby the coils of each pair D,, D,", D. D, and D,, D, are arranged in such a. mutual inductive relation as to compensate the diiierences in current. It obvious that instead of the three microphones illustrated in. Fig. 2, any number of microphones may be effectively connected in parallel in an analogous mannor.

In lieu of bringingthe choking coils into direct mutual inductive relation in the manner described. the arrangement illustrated in l i'g. 3 may hc selected. Here the primary coils D D,. D, influence inductively secondary coils (Z (7,, (Z, respectively which are so connected with each other (preferably in series to form a secondary circuit) that at a uniform inductive action, of coils D. 1),, D,

upon said secondary circuit. a current is generated which-will neutralize the self-induction of coils 1),, 1),, D Thus only thc above 'mentioned uneven operation of the microphones causes the geueratioii of a coinpensating current which equalizcs said irregularities. The connection illustrated in Fig. 3 has the advantage that the microphone circuits may he laid out independently of each other, while the coupling is effected through the compensating circuit.

I claim:

1. In a. device of the character described. a transmitting station comprising a pair of microphones connected n parallel. and mutually inductive current equalizing choking coils connected in series with said micro phones and located at the transmitting station.

In a device of the character described, 'a transmitting station comprising a. plurality of microphones connected in parallel, and mutually inductive choking coils connected in series with said microphones, the mutual inductive interrelation between said coils being such that with currents of equal strengths passing the microphones, the magnetizing effects of said currents are neutralized, while with currents of unequal strengths passing the microphones, an inductivc resistance is offered to the compensating currents flowing between the microphones.

3. In adevice of the character described 10 ductive interrelation coils being such that with currents of equal Gopies of this patent may'be obtained f between the several strengths passing the primary coils, it our rent is generated in the secondary circuit that neutralizes the self-induction of the primary coils, While with currents of un- 15 equal strengths passing the primary coils, an inductive resistance is offered to the current flowing in the secondary circuit.

RUDOLF GOLDSCHMIDT. \Vitnesses WOLDEMAR HAUPT, HENRY HAsrER.

M or five cents each, by addressing the "Commissioner of Patents,

Washington, D. C. 

